1. Field of the Invention
The present invention relates to a file management system for managing data of a plurality of files divided in a nonvolatile memory in a so-called IC card incorporating an IC chip having the nonvolatile memory and a control unit such as a CPU for controlling the nonvolatile memory and the like.
2. Description of the Related Art
In recent years, an IC card incorporating an IC chip having a nonvolatile data memory and a control unit such as a CPU for controlling the data memory and the like has received the great deal of attention as a portable data storage medium.
As described in U.S. Pat. No. 4,988,855 (Iijima), an IC card of this type divides an incorporated data memory into a plurality of files and stores data necessary for running a software application in each file. An application ID (identification) name is input from an external device to use selected or corresponding application data. For this reason, a plurality of application data are divided into files and stored in a single IC card, thus allowing multi-purpose applications.
The entire disclosure of U.S. Pat. No. 4,988,855 is incorporated in the present application.
A plurality of data files for storing data such as transaction data and a key file for storing key information for collating a password can belong to the above application files.
A file attribute called an access condition is set in each file. This access condition is determined by selectively designating a collation state of key information required at the time of access to the corresponding file. For example, when an access condition designates that the collation state of key information A in an IC card is required, key information A must be collated before this file is accessed.
Assume that a given application program is to access a file using a usable file discrimination ID number. For example, when this file is to be accessed using file discrimination ID number 1, file discrimination ID number 1 is set for the file, and key information A is collated using this file discrimination ID number 1, thereby allowing access to this file for the first time. Assume that another file discrimination ID number (e.g., discrimination ID number 2) is set by another external application. In this case, if the collation state of key information A which is established using file discrimination ID number 1 succeeds unconditionally, the above external application can access to the file, which requests the collation state of key information A, without collating key information A, thereby disabling security.